High reactance transformer



p 1944. L MAUERER; 2,358,725

HIGH REACTANGE TRANSFORIER Filed Sept 17. 1942 20 40 so an mfi fizzleizi'oz" leopuldffaaerei' Patented Sept. 19, 1944 HIGH BEACTANCB TRANSFORMER Leopold Mauerer,. 1iieago, 111.,

corporation of Illinois animosto Jefleraon Electric Company, Beliwood, 111., 1

Application September 17 1942, Serial No. 458,650

dclaima.

My invention relates to high reactance transformers and more particularly to a transformer a angement of this type having a high power factor characteristic over an extended operating range.

I Heretofore'in luminous tube lighting installa tions which present negative resistance characteristics as a load, high reactancetransformers have been designed sons to have relatively constant output characteristics. By utilizing an auxiliary winding and a capacitor it is possible to design a transformer arrangement of this type so that for a particular load the transformer will operate with a relatively high power factor. Conmiercial1y,.- however, the load usually differs from the particular load assumed in such design since there are variations in the tube lengths of th luminous signs and also variations in the gas pressures contained within the tubes, and therefore such transformers do not always operate with the desired high power factor. v

From a theoretical standpoint it ispossible to improve the power factor of transformers over a considerable operating range, but from a commercial standpoint this is not economically feasible because of the cost of the units involved in such design. present invention it is intended to provide to a considerable degree the desired characteristics in a high'reactance transformer arrangement which will operate over an extended range of loads as compared to'transformers now readily available on the market. In. accordance with my inventionthis is accomplished by providing a capacitive reactive effect which varies in accordance with different load values so as to tend to correct the power factor of the transformer, thereby extending the range over which operation may be obtained at a relatively high power factor.

Therefore it is an object of my invention to.

provide an improved transformer arrangement having limited current output characteristics which may be assembled in a unit economical to manufacture and which will overcome certain aforementioned disadvantages of the prior art.

Stillanother object of my invention is to prov de an improved transformer arrangement of the type having iimited current output characteristics which will provide relatively high power factor operation over an extended range of load values.

A further object of my invention is to pro- Accordingly by means of thevide a high reactance limited output current transformer with a. capacitive reactance the effective value of which varies in accordance with different conditions.

Another further object of my invention is to provide an improved transformer arrangement having a, limited current mid-point grounded secondary winding which will provide high power factor operation over an extended load range.

A: still further object of my invention is to provide a high reactance transformer arrangement which when connected to a power line having harmonics will reduce to a negligible degree the tendency thereof to reduce the power factor. Other and further objects of my invention will become more readily apparent by reference to the following description taken in connection with the drawing wherein:

Fig. 1 represents the physical arrangement of the magnetic core structure and the winding thereon of one embodiment of my invention;

Fig. 2 shows the electrical circuit arrangement a used with a transformer of the type shown in Fig. 1;

Fig. 3 represents another physical arrangement of a transformer structure;

Fi 4 is an electrical circuit arrangement utilizing the structure of the transformer shown in Fig. 3; and

Fig. 5 is a graphical representation illustrating the improved operational characteristics oh tained in accordance with the teaching of the present invention.

Referring more particularly to Figs. 1 and 2 it will be seen that there has been provided a magnetic core structure ii having magnetic shunt portions 1 and 8. Positioned centrally on th core structure 6 is a primary coil 9 and on the leg opposite the one on which this coil is mount= edthere is provided an auxiliary coil 5 I so that this coil has a magnetic flux path common to that of the coil 9. Separated by the magnetic shunt portions 7 and 8 are a pair of secondary coils l2 and it which are connected so as to provide a mid-point grounded secondary winding it. The auxiliary winding II is connected to the primary winding 9 so as to be in additive relation thereto. A capacitor 15 is connected across the windings ii and ii. The resultant circuit isthen connected by means of the terminals It to a suitable source of electric power. From the physical arrangement, of the coils 9 and II it will be seen that a common magnetic path is provided therefor, but that a close coupling of these two windings has been avoided.

Because of this arrangement the total effective capacitive reactance provided by the capacitor l and the leakage reactance between coils 9 and H is not a constant effective quantity but one which varies in accordance with the load. Due to the arrangement which avoids close coupled coils 9 and N there is also obtained improved operation where the terminals IB are connected to a power line having harmonics therein, since the efiective capacitive reactance provided by this arrangement is reduced at the higher harmonic frequencies thereby negativing the effects of harmonics which tend to reduce the power factor of the transformer arrangement. By providing the magnetic shunt paths 1 and 8 between the primary coil 9 and the secondary coils l2 and |3 the transformer has a high leakage characteristic so that the secondary current available across the terminals I4 is limited in value, thereby making this transformer arrangement particularly suitable for operation with luminous tube lighting which gener--' ally presents a negative resistance characteristic load.

Referring to Figs. 3 and 4 there is shown another transformer arrangement comprising a core H which is relatively narrow and elongated and which has magnetic shunt portions I8 and I9. Positioned centrally on the core is a primary coil 2| and adjacent each end of this primary coil is one of the auxiliary coil portions 22 and 23 so that the auxiliary coil portions have a magnetic path which is common to the primary coil 2|. Separated by magnetic shunt portions I8 and I9 from the primary and auxiliary coils there are provided secondary coils 24 and 25. The secondary coils 24 and 25 are connected to form midpoint grounded secondary winding arranged to supply power to a pair of terminals 26. The primary winding is connected by means of terminals 21 to a suitable source of alternating current. The auxiliary coils- 22 and 23 are connected in series with each other and to a primary coil 2| so as to be in additive relation thereto. A capacitor 28 is connected across the primary coil 2| and the secondary coils 22 and 23. From the arrangement of the primary and auxiliary coils it will be seen that a close coupling between the two windings has been avoided thereby providing an arrangement which in operation causes the effective capacitance of the capacitor 28 to vary in accordance with load conditions. By separating the secondary winding by magnetic shunt portions from the primary and auxiliary windings there is provided a high leakage reactance characteristic which limits the current output of the transformer to the desired load current value.

The improvement in the operational characteristics obtained by my invention heretofore described is best illustrated in Fig. 5 in which the percent of power factor has been plotted against the percent of short circuit current available across the secondary winding. The dotted line curve 29 illustrates a power factorcharacteristic obtained where an auxiliary winding and capacitor are provided and where the auxiliary winding is closely or tightly coupled to the primary winding. The curve 3| illustrates the improved operational characteristic obtained by avoiding such tight coupling and by utilizing transformer arrangements such as shown and described herein. My improved transformer arrangement of the high reactance type is therefore particularly suitable for use over an appreciable range of load values including loads having negative resistance characteristics. Furthermore considerable improvement is obtained by the reduction of the tendency of power line harmonics to reduce the power factor.

While for thepurpose of illustrating and describing my invention certain specific embodiments have been shown and described it is to be understood that modifications may be made therein without departing from the spirit and scope of my invention as set forth in these appended claims.

What I claim as new and desire'to secure by Letters Patent of the United States is:

1. A high leakage reactance transformer comprising an elongated magnetic core structure having at the center thereof a primary coil, an auxiliary coil mounted on said core structure symmetrically with respect to said primary coil, one

end of said auxiliary coil being connected to the adjacent end of said primary coil, a capacitor connected between the other ends of said coils, and' two secondary coils arranged symmetrically with respect to said other coils, said core structure having high leakage reactance paths between said secondary coils and said first mentioned coils.

2. A high power factor transformer comprising an elongated core structure having thereon a primary coil, an auxiliary coil symmetrical with respect thereto so as to have a magnetic core path common therewith, a pair of secondary coils each separated from said first coils by a magnetic shunt path, said secondary coils being connected to form a mid-point grounded secondary winding, said auxiliary coil being connected at one end in additive relation to one end of said primary coil, and a capacitor connected between the other ends of said primary and auxiliary coils to improve the power factor over an extended range of load values.

3. A high leakage reactance transformer arrangement comprising an elongated magnetic core structure, a primary coil centrally mounted thereon, a pair of auxiliary coils each mounted adjacent one end of said primary coil, two secondary coils each separated from the aforementioned coils by a magnetic shunt portion, said to one end of said primary coil, and a capacitor connected between the remaining ends of said primary and auxiliary coils.

4. A high leakage reactance transformer comprising an elongated core structure having centrally mounted thereon a primary coil, two secondary coils each mounted so as to be separated from said primary coils by a magnetic shunt core portion, said secondary coilsbeing connected to form a mid-point grounded secondary winding, an auxiliary coil mounted on said core on a leg opposite said primary coil and being serially connected in additive relation therewith, and a capacitor connected between the remaining ends of said primary and auxiliary coils to improve the power factor and to negative the effects of harmonics in the power source connected to the primary winding.

LEOPOLD MAUERER. 

